A serious problem all over the world is handling waste water resulting from sewage treatment facilities. Cities are becoming larger and larger and accordingly are generating increasing quantities of sewage waste water that must be properly treated before it is released to the environment. A standard technique for treating municipal sewage is to pass the sewage into a digester system wherein the sewage is reacted with bacteria to break down the organic components. After complete reaction with bacteria the result under ideal condition is a relatively clear effluent, the non-digestible components such as dirt, sand and so forth settling out as sludge that is permitted to dry and then disposed of. Such sludge makes good landfill and is otherwise readily disposed of.
A more serious problem is disposition of the resultant water effluent after treatment in a digester. While the organic action in a digester usually results in substantially complete decomposition of organic matter, nevertheless the resultant effluent can contain bacteria that can be harmful to aquatic life as well as animals and humans. Standard procedures for treating municipal waste in digesters frequently result in production of effluent that contains coliforms, that is, E-coli type bacteria that can be a serious environmental hazard.
The presently used procedure for treating the effluent from a municipal waste digester is to inject chlorine into the effluent for discharge to the environment. While chlorine is successful in killing any remaining bacteria and particularly killing coliforms, the chlorine itself is becoming an environmental problem. Because of the huge amounts of municipal waste effluent that is treated by chlorine that is constantly released to the environment, including into the atmosphere, some authorities are beginning to impose restrictions on the amount of chlorine that can be contained within discharged effluent. Putting it another way, some governmental agencies have enacted specifications defining effluent suitable for environmental discharge to substantially eliminate the use of chlorine. Most plants which put effluent back into the environment are to dechlorinate the effluent first. This doubles the cost of disinfecting the effluent and then dechlorinating.
This invention provides a method of treating sewage waste water that results from a sewage digester system to make the sewage waste water acceptable for discharge into the environment, such as a lake, stream, ocean or the like, and which does not include entrained chlorine.
Others have provided systems and processes for treating municipal waste in an effort to provide an effluent discharge that is environmentally acceptable. As an example, U.S. Pat. No. 4,188,289 that issued Feb. 12, 1980 entitled "Process For Purification Of Sanitary Water", Ferdinand Besik, inventor, teaches a relatively complex system employing a series of various biochemical and chemical reactions including the use of a fluidized reactions that take place in a fluidized non-biodegradable suspended solid solution. The system includes chemical oxidation for providing removal of remaining impurities and the killing of bacteria and viruses. However, the system involves a relatively complex sequence of steps so that the system would be inheritantly difficult to monitor and control.
U.S. Pat. No. 4,204,955 issued May 27, 1980 is entitled "System For Pollution Suppression", Edward T. Armstrong, inventor. This patent teaches a process in which air, oxygen-enriched gas, or oxygen itself is ozonated and the system operates in a way to provide increased concentration of ozone that is fed to a fluid dispersing system containing a flat plate orifice which creates a down stream vena contracta. The addition of the ozonated gas into the vena contracta produces an efficient mixing device, however the overall system is complex and the equipment required to carry out the process is therefore relatively expensive compared with the simplicity and economy of operation of the process that is to be revealed in this disclosure.
U.S. Pat. No. 4,370,306 issued Jan. 25, 1983 is entitled "Process For Separation of Traces of Gaseous Contaminants From Waste Gases By Chemical Absorption", Kurt Kirchner and Wolfgang Litzenburger, inventors. The process disclosed in this patent is useful for separation of traces of gaseous contaminants or pollutants that are based on halogens, sulfur or other compounds. The process that is taught in this patent is not helpful in finding a way to avoid the commonly employed use of chlorine to kill bacteria that is typically entrained in a sewage treatment discharge effluent and therefore does not solve the problem that is solved by the present invention.
U.S. Pat. No. 4,416,786 issued Nov. 22, 1983 is entitled "Process For The Treatment of Continuous Waste Water Streams Having Changing Contents of Different Oxidizable Materials With Hydrogen Peroxide", Helmut Knorre, Joachim Fischer and Klaus Stutzel, inventors. This patent is concerned with a process for the treatment of a continuous waste water stream having a varying content of oxidizable materials wherein the oxidizable materials are treated with hydrogen peroxide for the purpose of detoxification and reduction of the chemical oxygen demand and biological oxygen demand. This patent further includes a method of regulating the rate of administration of hydrogen peroxide. The system is relatively complex and does not achieve the economy, efficiency and simplicity of the system of this invention for treating waste water.
For additional background information relating to efforts of others to improve waste water treatment, the disclosures contained in the following United States patents are helpful.
______________________________________ U.S. PAT. NO. INVENTOR TITLE ______________________________________ 4,612,124 Escrig Method of Sewage Treatment 5,037,624 Tom et aI Composition, Apparatus and Process, For Sorption of Gaseous Compounds of Group II-VII Elements 5,132,383 Larson et al Copolymers of 3- Methacryloyloxy-2- Hydroxypropyl Trimethylammonium Chloride Monomer and Vinyl Monomer 5,167,806 Wang et al Gas Dissolving and Releasing Liquid Treatment System 5,240,600 Wang et al Water and Wastewater Treatment System 5,433,858 Elliott, Jr. Treatment of Hazardous Waste Water 5,470,480 Gray et al Process For Treating Waste Water Effluent 5,503,720 Teske Process For The Quantitative Determination of Electrochemically Reducible or Oxidizable Substances, Particularly Peracetic Acid Mixed With Other Oxidizing Substances ______________________________________